When selecting a deep groove ball bearing for a new design or replacement, engineers often ask: What are the exact dimensions of a 6004 bearing? What is the difference between 6004 ZZ and 6004 2RS? And can this bearing handle the required speed and load conditions? This guide provides a comprehensive overview of the 6004 bearing, covering its dimensions, composition, characteristics, sealing options, and typical applications.
What Are the Dimensions of a 6004 Bearing?
The 6004 bearing follows standard metric dimensions that are consistent across manufacturers worldwide, including major international brands. This standardization ensures dimensional interchangeability, making the 6004 bearing a reliable choice for both OEM applications and maintenance replacements.
6004 Bearing Dimensions Table (ISO 492)
| Parameter | Millimeter (mm) | Inch (in) | Tolerance (P0/ABEC 1) |
|---|---|---|---|
| Inner diameter (d) | 20 mm | 0.7874 in | 0 / -0.010 mm |
| Outer diameter (D) | 42 mm | 1.6535 in | 0 / -0.011 mm |
| Width (B) | 12 mm | 0.4724 in | 0 / -0.120 mm |
| Fillet radius (r min) | 0.6 mm | 0.024 in | ±0.2 mm (max) |
The 6004 bearing is classified as an Extra Light series bearing within the 6000 metric series, making it suitable for applications where space constraints are a consideration.
What Is a 6004 Bearing Composed Of?
Like all single row deep groove ball bearings, the 6004 bearing consists of four fundamental components:
- Inner ring — Fits onto the shaft and rotates with it
- Outer ring — Fits into the housing and provides stationary support
- Rolling elements (balls) — Reduce friction by rolling between the inner and outer rings
- Cage (retainer) — Maintains proper spacing between balls and guides their rotation
The inner and outer rings of a 6004 bearing are manufactured from high-carbon chromium bearing steel, typically GCr15 (AISI 52100 equivalent). After heat treatment, the material achieves a hardness of HRC60–64, providing wear resistance and the ability to withstand substantial loads. The rolling elements are made of the same bearing steel with a hardness of HRC61–66 after heat treatment.
Cages are typically constructed from pressed steel, though some variants use polyamide (nylon) cages for reduced weight and improved lubrication distribution. Steel cages offer high rigidity and strength, while polymer cages can reduce friction and noise in certain applications.
Key Characteristics and Performance Specifications
The 6004 deep groove ball bearing is engineered for reliable operation across a broad range of conditions. Its design features a deep raceway geometry that allows the bearing to accommodate both radial loads and moderate axial loads in either direction.
Load Ratings (Typical Values)
| Parameter | Value |
|---|---|
| Dynamic load rating (Cr) | 9.4 kN |
| Static load rating (Cor) | 5.0 kN |
| Fatigue load limit | 0.36 kN |
The dynamic load rating of 9.4 kN indicates the load level at which the bearing can achieve a rated service life of one million revolutions. The static load rating of 5.0 kN represents the maximum load the bearing can withstand without permanent deformation.
Speed Capabilities
| Lubrication Type | Limiting Speed (rpm) |
|---|---|
| Grease lubrication | 16,000–18,000 rpm |
| Oil lubrication | 19,000–21,000 rpm |
The actual maximum operating speed depends on factors including lubrication type, load magnitude, and thermal conditions. Sealed or shielded variants typically have lower permissible speeds than open bearings due to increased friction from the seal or shield.
Material and Operational Features
The 6004 bearing is manufactured from high-quality GCr15 bearing steel, which provides excellent durability, dimensional stability, and precision. Key performance characteristics include:
- Low friction due to point contact between balls and raceways
- Low noise and low vibration operation
- Capability for high-speed rotation
- Suitability for light to moderate radial and axial loads
- Simple, robust design requiring minimal maintenance
The deep groove geometry enables the bearing to handle bidirectional axial loads — typically about one-third to one-half of its radial capacity.
6004 Bearing Code Meaning Explained
The bearing industry uses a standardized numbering system that encodes key information about the bearing type and dimensions. For the 6004 bearing, the code breaks down as follows:
| Digit | Meaning | Explanation |
|---|---|---|
| 6 | Bearing type | Single row deep groove ball bearing |
| 0 | Series / Width | Extra light series (6000 series) |
| 04 | Bore size | 04 × 5 = 20 mm inner diameter |
In the ISO bearing numbering system, the bore size is calculated by multiplying the last two digits by 5. Thus, “04” × 5 = 20 mm bore diameter. This calculation applies to bearings with bore diameters between 20 mm and 480 mm.
Sealing Types: Open, ZZ, and 2RS
The 6004 bearing is available in several sealing configurations, each suited to different operating environments. The suffix code following the base number indicates the sealing type.
Open Type (No suffix)
Open bearings have no seals or shields on either side. The internal components remain fully exposed. Open bearings offer the lowest friction and highest speed capability, making them suitable for high-speed applications where the bearing housing provides adequate environmental protection and external lubrication is available.
ZZ Type (Metal Shields)
6004 ZZ bearings have a non-removable metal shield pressed into the outer ring on both sides. These shields are typically made of stainless steel or strip steel and maintain a small running clearance with the inner ring. ZZ bearings offer:
- Low friction, comparable to open bearings
- Good protection against larger dust particles
- Limited defense against fine dust or moisture
- No waterproofing capability
- Maximum operating temperature up to 450°F (230°C) for steel shields
2RS Type (Rubber Seals)
6004 2RS bearings feature molded rubber seals bonded to a steel insert on both sides. The seal lip makes light contact with a groove on the inner ring. Rubber seals provide:
- Superior protection against dust, moisture, and fine contaminants
- Better waterproofing compared to metal shields
- Higher friction than open or shielded bearings
- Lower maximum speed capability than ZZ or open bearings
- Maximum operating temperature approximately 240°F (115°C) for standard Buna-N seals
Comparison Summary:
| Feature | Open | ZZ (Double Shield) | 2RS (Double Seal) |
|---|---|---|---|
| Friction | Lowest | Low | Moderate to High |
| Speed capability | Highest | High | Moderate |
| Dust protection | None | Moderate | Excellent |
| Moisture protection | None | Poor | Good |
| Maintenance | Requires relubrication | Pre-greased, low maintenance | Pre-greased, sealed for life |
Common Applications of the 6004 Bearing
Due to its versatile design and balanced performance characteristics, the 6004 bearing is used across numerous industries. The bearing supports rotating components such as wheels, motors, fans, and drums, ensuring smooth operation and reliable performance.
Automotive
In the automotive sector, the 6004 bearing is employed in auxiliary electric motors, cooling fans, small transmission components, and water pumps. Both shielded (ZZ) and sealed (2RS) versions are used depending on the level of contamination protection required.
Industrial Machinery
The 6004 bearing appears in conveyors, pumps, gearboxes, and general industrial equipment. Its ability to handle both radial and moderate axial loads makes it suitable for many mechanical assemblies. The open variant is often preferred when external lubrication systems are available.
Electric Motors
Electric motors represent a primary application for the 6004 bearing, particularly fractional horsepower motors found in fans, blowers, and small machinery. The low noise and low vibration characteristics of the 6004 bearing are especially valued in motor applications.
Household Appliances
Washing machines, fans, power tools, and various domestic electrical devices utilize the 6004 bearing to provide smooth rotational movement while reducing friction and operational noise.
Agriculture
Agricultural equipment such as small harvesters, conveyors, and irrigation pumps frequently employ 6004 bearings, often in sealed variants to protect against dust and moisture exposure.
Skateboards and Bicycles
The 6004 bearing is commonly found in the wheels of skateboards, inline skates, and some bicycle components. The low-friction design contributes to smooth rolling and extended glide performance.
Conclusion
The 6004 bearing is a standard deep groove ball bearing with an inner diameter of 20 mm, an outer diameter of 42 mm, and a width of 12 mm. Manufactured from GCr15 bearing steel with a hardness of HRC60–64, it offers reliable performance for high-speed rotation and moderate radial and axial loads.
Three sealing configurations are available to suit different environments: open type for clean, high-speed applications; ZZ (metal shielded) for general dust protection; and 2RS (rubber sealed) for superior moisture and contaminant resistance.
When selecting a 6004 bearing for a specific application, consider the operating environment, required speed, load conditions, and maintenance accessibility to choose the appropriate sealing configuration.
Frequently Asked Questions (FAQs)
Q1: What is the difference between a 6004 bearing and a 6204 bearing?
A1: The 6004 bearing measures 20×42×12 mm (inner diameter × outer diameter × width), while the 6204 bearing measures 20×47×14 mm. The larger outer diameter and width of the 6204 provide approximately 45% higher load capacity. The 6004 is classified as an Extra Light series bearing, whereas the 6204 belongs to the Light series.
Q2: What does the suffix C3 mean in a 6004 bearing?
A2: C3 indicates that the bearing has greater internal radial clearance than the standard CN (normal) clearance. C3 clearance is selected when thermal expansion of the shaft or housing is expected, or when the bearing operates at high speeds where heat generation may reduce clearance during operation.
Q3: Is there a difference between 6004 ZZ and 6004 2RS?
A3: Yes. 6004 ZZ uses metal shields on both sides, offering low friction and good dust protection but no waterproofing. 6004 2RS uses rubber seals on both sides, providing superior protection against moisture and fine contaminants but with higher friction and lower maximum speed capability.
Q4: What is the maximum speed of a 6004 bearing?
A4: Under grease lubrication, the limiting speed ranges from 16,000 to 18,000 rpm. Under oil lubrication, speeds of 19,000 to 21,000 rpm are achievable. Actual operating speed depends on load conditions, lubrication method, and bearing sealing type.
Q5: How do I properly install a 6004 bearing?
A5: Apply pressure only to the ring being mounted — press the inner ring onto the shaft and the outer ring into the housing. Never apply mounting force through the rolling elements. Ensure proper alignment and use clean, appropriate tools to prevent damage to raceways and balls.
Q6: What lubricant should I use for a 6004 bearing?
A6: For open bearings, use a lithium-based grease meeting NLGI Grade 2 consistency, or high-quality circulating oil for high-speed applications. Sealed bearings come pre-greased from the factory and typically do not require relubrication.
Q7: Can 6004 bearings from different manufacturers be interchanged?
A7: Yes. The 6004 bearing follows international standardization (ISO 492), ensuring dimensional interchangeability across manufacturers. However, load ratings and internal designs may vary slightly.
Q8: What are the static and dynamic load ratings of a 6004 bearing?
A8: The static load rating (Cor) is 5.0 kN, representing the maximum load before permanent deformation occurs. The dynamic load rating (Cr) is 9.4 kN, representing the load for a rated life of one million revolutions.
